Many refrigeration and air conditioning systems, especially residential and mobile systems, have threaded fittings in which a threaded check valve core is installed to provide access to the system. Such threaded check valves are of the type commonly used in automobile tire valve stems and are often referred to as "Schrader" type (depressing) valve cores. Most have no shut-off valves, thus allowing a loss of refrigerant when connecting or disconnecting charging hoses, which results in unsafe, wasteful and harmful emissions into the atmosphere (causing, e.g., ozone depletion), in addition to unbalanced refrigerant charges in the system which causes the system to be inefficient. Present systems do not allow the independent vacuum process of both the condenser and evaporator section of the system simultaneously.
Other common problems, in the proper maintenance and repair of refrigeration systems, are the means to check the system to determine the location of leaks and the inability to perform repairs or other work on the condenser unit without "blowing the charge" or venting the refrigerant charge into the atmosphere.
The prior art contains a number of teachings of servicing tools and/or means to provide access to a closed refrigeration system, e.g., those disclosed in U.S. Pat. No. 3,935,713 issued to John W. Olson (1976), U.S. Pat. No. 3,916,947 issued to Paul M. Holmes (1975), U.S. Pat. No. 3,785,163 issued to William Wagner (1974), and U.S. Pat. Nos. 3,916,641 and 3,996,765 both issued to John W. Mullins (1975).
The Olson patent discloses an external tool for the removal of Schrader type (depressing) valves. It is not installed in the system and does not have a main flow shut-off valve and it does not contain a by-pass mechanism to gain access to the system.
The device of the Holmes patent has an access port with a Schrader valve, which the preferred embodiment of this invention eliminates. It does not have a shut-off valve on the access port. The valve access is not upstream of the main shut-off valve and, therefore, a technician cannot isolate the refrigerant upstream of the main shut-off valve to perform a by-pass operation. It also has only one shut-off valve in the refrigerant flow line.
The Wagner patent discloses a refrigerant charging means and method for charging a saturated vapor refrigerant into the low pressure side of a refrigeration or air conditioning system. It discloses a portable external device which is not installed in the system, either at the factory or on-site at the location of the unit. It is a method of metering the charge. It does not allow a by-pass operation and does not allow the isolation of the evaporator or condenser sections of the systems in order that the location of leaks may be more easily ascertained.
The Mullins patents disclose a spring and cam shaft to depress a valve core, a Schrader valve, which can be eliminated in the preferred embodiments of the present invention. The Mullins patents disclose a portable external tool or device which is not an in-the-unit system and which does not have a double valve that allows a by-pass operation.
The present invention addresses and solves the above mentioned problems, when used with the prescribed techniques, and provides other advantages over the present means which will be further discussed below.